Process and apparatus for producing iron carbide

ABSTRACT

Iron carbide is produced by an apparatus comprising first fludized bed reactor  4  and second fluidized bed reactor  5 , wherein the charged grainy iron oxide is reduced and carburized by the high temperature and high pressure gas being introduced from the bottom of the reactor. Both fluidized bed reactors comprise chamber  23  for introducing gas into the reactor, distribution plate  27  having multiple gas-introducing nozzles  28 , partition plate  26  partitioning the fulidized bed into plural division rooms, and gas supply inlet  25   a   , 25   b  arranged on chamber  23  for supplying gas to specific division room respectively. Each gas supply inlet is connected to gas supply line having a gas flow control valve for controlling gas pressure or gas flow rate.  
     There is provided with a gas circulation loop having a quenching tower  10   a,   10   b  and cooler  12   a,    12   b  which eliminate dust contained in the exhaust gas of the reactor, and having a preheater  15   a,    15   b  for heating the gas, wherein the exhaust gas is returned to the chamber by way of quenching tower, cooler and preheater.  
     Using the above apparatus, a grainy iron oxide is reacted with gas and iron carbide is produced by the steps of;  
     charging a grainy iron oxide from a side wall of fluidized bed reactor  4, 5;    
     reducing and carburizing the grainy iron oxide under floating and fluidizing by high temperature and high pressure gas being introduced from the bottom of the reactor;  
     transferring the grainy iron oxide from the division room of the upstream side to the division room of the downstream side via a communication space located at either upper or lower part of the partition plate under fluidizing;  
     discharging produced iron oxide from the final division room.

TECHNICAL FIELD

[0001] The present invention relates to a process and apparatus forproducing iron carbide.

BACKGROUND ART

[0002] A traditional method for producing steel from iron oxide such asiron ore normally comprises the steps of;

[0003] in the first step, producing molten pig iron in such a mannerthat coke produced at a coke oven, other raw materials and iron oxideare charged into a blast furnace, and thereafter, iron oxide are moltenand reduced by combustion heat of carbon contained in coke generated dueto blowing of high temperature oxygen and carbon monoxide generated dueto combustion of said carbon;

[0004] in the second step, charging the molten pig iron into aconverter, and converting the molten pig iron by oxygen blowing intosteel, wherein a carbon concentration of which is under the demandedvalue.

[0005] Since such traditional steel making process by a blast furnacerequires many ancillary facilities such as coke oven, sintering furnace,and air-heating furnace, equipment cost becomes high. Furthermore, thissteel making process via a blast furnace requires the expensive coalsuch as high coking coal and huge site for many facilities and rawmaterials storage. Therefore, recently, to overcome the abovedisadvantages of using a blast furnace, new iron making processes,instead of a blast furnace, have been developed and put to practicaluse.

[0006] For example, one of the newly developed processes for producingsteel is a method called as iron carbide-electric furnace process. Thisprocess comprises the steps of obtaining iron carbide by reacting grainyiron oxide with a reducing agent such as hydrogen and a carburizingagent such as methane gas, and producing steel by smelting said ironcarbide at an electric furnace. A fluidized bed reactor is a well knownapparatus for producing iron carbide. The laid open publication No. HEI6-501983, which is the publication of the Japanese translation ofInternational Patent Application No. PCT/US91/05198 discloses anapparatus for producing iron carbide. As shown in FIG. 8, saidpublication shows an apparatus for producing iron carbide, wherein whena grainy iron oxide is charged into fluidized bed reactor 32 via inlet31, the grainy iron oxide is reduced under floating and fluidizing dueto the high temperature and high pressure gas being introduced frommultiple nozzles 33 located in the bottom portion of the reactor.Thereafter, the iron oxide is broken into smaller pieces as a result ofthe foregoing reaction and moves along with a passage formed bybaffle-plates 34, 35, 36, 37, and is finally discharged as iron carbidefrom outlet 38. (Hereinafter, this apparatus is called as prior art.)

[0007] By the way, the reaction for converting iron oxide into ironcarbide proceeds as shown in the following formulas (1) through (6).

Fe₂O₃+3H₂→2Fe+3H₂O

(FeO_(1.5+)1.5H₂→Fe+1.5H₂O)   (1)

Fe₃O₄+4H₂→3Fe+4H₂O

(FeO_(1.3)+1.3H₂→Fe+1.3H₂O)  (2)

Fe₃O₄+H₂→3FeO+H₂O  (3)

FeO+H₂→Fe+H₂O  (4)

3Fe+CH₄→Fe₃C+2H₂  (5)

3Fe₂O₃+5H₂+2CH_(4→)2Fe₃C+9H₂O  (6)

[0008] As shown in the above formulas (1) through (6), the iron oxide isconverted into iron carbide in turn of Fe₂O₃, Fe₃O₄, FeO, Fe and Fe₃C,and the volume of the reducing gas H₂ to be used varies according toeach stage in the reducing reaction. On the other hand, under some gastemperature or some gas composition, there is such a case that FeO isnot generated. As is described below, the prior art has the variousproblems to be solved.

[0009] First, the higher the concentration of methane and carbonmonoxide contained in the reducing and carburizing gas becomes, thefaster the carburizing reaction proceeds. But when the concentration ofmethane and carbon monoxide contained in said reaction gas becomesexcessively high, a fixed carbon is generated from the reaction gas dueto the reaction as shown in the following formulas (7) and/or (8).

[0010] As a result, extra reaction gas is uselessly consumed.Furthermore, the fixed carbon has such a bad effect upon the gascirculation loop as to be turned into dust and sticked on a tube of gasheater.

CH₄→C(fixed carbon)+2H₂  (7)

2CO→C(fixed carbon)+CO₂  (8)

[0011] At the most vigorous stage of the reaction, the reducing reactionby hydrogen is conducted vigorously as is described above, and the watervapor generated by said reducing reaction prevent the generation offixed carbon. But, at the final stage of the reaction, since littlewater vapor for preventing the generation of fixed carbon is generated,the fixed carbon is liable to easily generate.

[0012] There are two means to prevent the generation of fixed carbon.One is to decrease the concentration of methane and carbon monoxidecontained in the reaction gas, and the other is to increase theconcentration of water vapor contained in the reaction gas. But thosemeans result in the decline of the reaction speed, namely, the loweringof the productivity.

[0013] The higher the gas temperature becomes, the faster the reactionspeed becomes. But, when the temperature of the fluidized bed comes tobe over about 600° C. (for example, 570° C.˜590° C.) due to theexcessively high temperature gas, the iron oxide remained in the productof iron carbide is turned into not Fe₃O₄ whose chemical character isstable, but FeO whose chemical character is unstable.

[0014] If the reaction gas temperature is decreased so as to avoid theabove disadvantage, it will result in the decline of the reaction speed,namely, the lowering of the productivity.

[0015] Furthermore, as the reaction proceeds, the specific gravity ofiron oxide becomes lower and the diameter of iron oxide particles becomesmaller due to its own powdering. Therefore, the iron oxide particles atthe stage of the second half of the reaction is liable to fly. The ironoxide particles flown outside the reactor has the low carburizationdegree because of the short staying time at the reactor. As a result, itbrings the lowering of the average carburization degree of the productof iron carbide.

[0016] Consequently, it is preferable to regulate the flow velocity ofthe gas flowing through the fluidized bed according to the proceeding ofthe reaction. But it is impossible for the prior art to change the flowvelocity of the gas, unless applying some complicated works, such asalternating the resistance of the gas blowing nozzle installed at thegas distribution plate.

[0017] Furthermore the method for producing iron carbide, which ischaracterized by that the reducing reaction is partially conducted in afirst stage reactor, then the further reducing and carburizing reactionis conducted in a second stage reactor, is known.

[0018] But in this method, the control of reduction degree of the oredischarged from the first stage reactor is necessary. It is possible tocontrol the reduction degree by altering the gas flow rate, the gastemperature or the gas composition. Said altering, however, is not easybecause the quantity of gas to deal with is so much. As a result, itpresents the difficulty in controlling conformably and carefully thereduction degree.

[0019] The above-mentioned disadvantages of the prior art for producingiron carbide will be easily overcome by the present invention.

[0020] The objective of the present invention is to provide a processand apparatus for producing effectively iron carbide having thechemically stable components.

DISCLOSURE OF INVENTION

[0021] An object of this invention is to provide a process for producingiron carbide by an apparatus having constitution elements (a) to (e);

[0022] (a) a fluidized bed located at an upper part within a fludizedbed reactor, and, p0 (b) a chamber located at a lower part within thereactor to work as a gas header for introducing a reducing andcarburizing gas;

[0023] wherein the fluidized bed and the chamber are separated intoupside and downside by a distribution plate on which multiple gasintroducing nozzles are installed; and the fluidized bed located at anupper part of the distribution plate is partitioned into plural divisionrooms which are formed in isolated or mazy room by a partition plate;and,

[0024] (c) plural gas supply inlets arranged on the chamber forsupplying gas respectively to the specific division room, and,connecting a gas supply line to each gas supply inlet in order to supplya reducing and carburizing gas,

[0025] wherein each gas supply line has a gas flow control valve whichcontrols gas pressure or gas flow rate; and,

[0026] (d) one or more than two of gas circulation loop having aquenching tower and a cooler which eliminate dusts contained in theexhaust gas and reduce water vapor contained in the exhaust gas, andhaving a preheater for heating the gas,

[0027] wherein the exhaust gas is returned to the chamber by way of thequenching tower, cooler and preheater; and,

[0028] (e) a gas supplying apparatus through which hydrogen gas andcarbon-containing gas such as methane are supplied to a gas circulationloop; and further, comprising steps for reacting grainy iron oxidecharged from a side wall of the reactor with the gas in such a mannerthat;

[0029] the iron oxide is floated and fluidized by high temperature andhigh pressure gas being introduced form the bottom portion of thereactor, and then, transferred from the division room of the upstreamside to the division room of the downstream side via a communicationspace which may locate at either upper or lower part of said partitionplate, and finally, produced iron carbide is discharged from the finaldivision room.

[0030] Another object of the present invention is to provide a processfor producing iron carbide, wherein a chamber is separated into pluralparts by separation plate and each separated part comprises anindividual gas supply inlet respectively.

[0031] Another object of the present invention is to provide a processfor producing iron carbide, wherein a separation plate is installed atthe upper part of the chamber in such a manner that only the upper partof the chamber is divided into plural parts by said separation plate.

[0032] Another object of the present invention is to provide a processfor producing iron carbide, wherein a separation plate is installed fromthe top of the chamber to the bottom thereof for isolating eachseparation part.

[0033] Another object of the present invention is to provide a processfor producing iron carbide, wherein a separation plate is installed fromthe top of the chamber to the bottom thereof for separating the chamberinto plural parts, and the separated parts are communicated each othervia an aperture arranged on the separation plate.

[0034] Another object of the present invention is to provide a processfor producing iron carbide wherein the amount of water vapor containedin the gas to be supplied to the division room of the downstream side ismade larger than that contained in the gas to be supplied to thedivision room of the upstream side.

[0035] Another object of the present invention is to provide a processfor producing iron carbide, wherein the amount of water vapor containedin the gas to be supplied to the division room of the downstream side isincreased by supplying water vapor from the outside of the reactor.

[0036] Another object of the present invention is to provide a processfor producing iron carbide, wherein the amount of water vapor containedin the gas to be supplied to the division room of the downstream side isincreased in such a manner that cooling operation of a quenching towerand a cooler in a gas circulation loop is regulated so as to decreasethe amount of removal of water vapor by said quenching tower and saidcooler.

[0037] Another object of the present invention is to provide a processfor producing iron carbide, wherein the hydrocarbon gas or the carbonmonoxide gas contained in the gas to be supplied to the division room ofthe downstream side is made smaller than that contained in the gas to besupplied to the division room of the upstream side.

[0038] Another object of the present invention is to provide a processfor producing iron carbide, wherein the amount of the hydrocarbon gas orthe carbon monoxide gas contained in the gas to be supplied to thedivision room of the upstream side is increased by supplying hydrocarbongas or carbon monoxide gas from the outside of the reactor more thanthat contained in the gas to be supplied to the division room of thedownstream side.

[0039] Another object of the present invention is to provide a processfor producing iron carbide, wherein the gas flow rate per unit area ofthe gas to be supplied to the division room of the downstream side ismade smaller than that of the gas to be supplied to the division room ofthe upstream side.

[0040] Another object of the present invention is to provide a processfor producing iron carbide, wherein the temperature of the gas to besupplied to the division room of the downstream side is made lower thanthat of the gas to be supplied to the division room of the upstreamside.

[0041] Another object of the present invention is to provide a processfor producing iron carbide, wherein the temperature of the gas to besupplied to the division room of the downstream side is made lower thanthat of the gas to be supplied to the division room of the upstream sidein such a manner that a low temperature gas is mixed with the gasdischarged from the preheater in the gas circulation loop.

[0042] Another object of the present invention is to provide a processfor producing iron carbide, wherein the low temperature gas is a part ofthe gas to be supplied to a preheater.

[0043] Another object of the present invention is to provide a processfor producing iron carbide, wherein the low temperature gas is suppliedfrom the outside of the reactor.

[0044] Another object of the present invention is to provide a processfor producing iron carbide, wherein the temperature of the fluidized bedin the division room of the downstream side is made in the range of500˜600° C.

[0045] Another object of the present invention is to provide a processfor producing iron carbide, wherein the temperature of the fluidized bedin the last division room of the downstream side is made in the range of500˜600° C. by decreasing the temperature of only the gas to be suppliedto the last division room of the downstream side.

[0046] Another object of the present invention is to provide a processfor producing iron carbide, wherein the temperature of the gas to besupplied to the division room of the downstream side is made lower thanthat of the gas to be supplied to the division room of the upstream sidein such a manner that oxygen is mixed with the gas to be supplied todivision room of the upstream side, and then, a part of combustible gascontained in said gas is partially burned in order to raise the gastemperature.

[0047] Another object of the present invention is to provide a processfor producing iron carbide, wherein the concentration of hydrogencontained in the gas to be supplied to the division room of the upstreamside is made higher than that of hydrogen contained in the gas to besupplied to the division room of the downstream side.

[0048] A still further object of the present invention is to provide aprocess for producing iron carbide, wherein the concentration of thehydrogen in the gas to be supplied to the division room of the upstreamside is increased by supplying hydrogen gas from the outside of thereactor.

[0049] Another aspect of this invention is to provide an apparatus forproducing iron carbide comprising the constitution elements (a) to (e);

[0050] (a) a fluidized bed located at an upper part within a fludizedbed reactor, and,

[0051] (b) a chamber located at a lower part within the reactor to workas a gas header for introducing a reducing and carburizing gas;

[0052] wherein the fluidized bed and the chamber are separated intoupside and downside by a distribution plate on which multiple gasintroducing nozzles are installed; and the fluidized bed located at anupper part of the distribution plate is partitioned into plural divisionrooms which are formed in isolated or mazy room by partition plate; and,

[0053] (c) plural gas supply inlets arranged on the chamber forsupplying gas respectively to the specific division room; and,connecting a gas supply line to each gas supply inlet in order to supplya reducing and carburizing gas;

[0054] wherein each gas supply line has a gas flow control valve whichcontrols each gas pressure or gas flow rate; and,

[0055] (d) one or more than two of gas circulation loop having aquenching tower and a cooler which eliminate dusts contained in theexhaust gas and reduce water vapor contained in the exhaust gas, andhaving a preheater for heating the gas,

[0056] wherein the exhaust gas is returned to the chamber by way of thequenching tower, cooler and preheater; and,

[0057] (e) a gas supplying apparatus through which hydrogen andcarbon-containing gas such as methane are supplied to said gascirculation loop.

[0058] H₂, CH₄, CO, CO₂ and H₂O and the like can be used as a reactiongas for the present invention.

[0059] The present process and apparatus for producing iron carbidehaving the above constructions demonstrates the following advantages.

[0060] That is to say, it can be conducted by the present invention thatthe gas conditions such as gas temperature, gas flow rate and gascomposition, which is introduced into the fluidized bed of iron oxideparticle inside the reactor, may not make fixed but partially changed.

[0061] Consequently, it is possible to lower the concentration ofmethane and carbon monoxide and raise the concentration of water vaporcontained in the gas introduced into the division room of the downstreamside in comparison with the concentration of those gases contained ingas introduced into the division room of the upstream side. It thus canbe achieved to maintain a high productivity operation under preventingthe generation of fixed carbon from the reaction gas.

[0062] It is possible to lower the gas temperature introduced into thedivision room of the downstream side in comparison with the gastemperature introduced into the division room of the upstream side. Itthus can be achieved to maintain a high productivity operation andproduce iron carbide having a small quantity of chemically unstablewustite and a large quantity of chemically stable magnetite.

[0063] Furthermore, it is possible to decrease the gas flow rateintroduced into the division room of the downstream side in comparisonwith the gas flow rate introduced into the division room of the upstreamside according to the decreasing specific gravity and particle diameterin accordance with the proceeding of the reaction. It thus can beachieved to decrease the iron oxide flown the outside the reactor andproduce iron carbide having a high average carburization ratio.

[0064] In case of conducting the reducing and carburizing reaction usingtwo reactors, it is easy to alter the gas flow rate, the gas compositionand/or the gas temperature because the gas quantity introduced into thedivision room of the fluidized bed at the final reaction stage of thefirst reactor is smaller than the whole gas quantity. It thus can easilybe achieved to control the reduction degree of iron oxide includingmetallic iron discharged from the first reactor.

[0065] Furthermore, by the present invention, it can be accomplished toprevent the generation of fixed carbon from the reducing and carburizinggas and allow the kind of iron oxide remaining in the product of ironcarbide to be magnetite whose chemical character is stable. It also canbe accomplished to decrease the quantity of iron ore particle flownoutside the reactor.

[0066] As a result, the present invention can provide a process andapparatus for producing effectively iron carbide with the high operationratio and the low production cost.

BRIEF DESCRIPTION OF DRAWINGS

[0067]FIG. 1 is a process flow diagram showing example of the entireconstruction of a process for producing iron carbide of the presentinvention.

[0068]FIG. 2 shows an example of a supply passage of makeup gas.

[0069]FIG. 3 is a figure showing an example of a fluidized bed reactor.

[0070]FIG. 3(a) shows a longitudinal sectional view of a fluidized bedreactor whose fluidized bed is partitioned into two parts

[0071]FIG. 3(b) shows a sectional view at the line III-III of FIG. 3(a).

[0072]FIG. 4 is a figure showing the change of the amount of watergenerated by the reducing reaction of iron oxide during the batch test.

[0073]FIG. 5 is a figure showing the change of the amount of hydrogenconsumed by the reducing reaction of iron oxide during the batch test.

[0074]FIG. 6 is a longitudinal sectional view showing an example of thelower part of the fluidized bed reactor of the present invention.

[0075]FIG. 7 is a longitudinal sectional view showing an another exampleof the lower part of the fluidized bed reactor of the present invention.

[0076]FIG. 8 shows a plan view of an example of conventional fluidizedbed reactor.

[0077]FIG. 9 shows a sectional view at the line IX-IX of FIG. 8.

BEST MODE FOR CARRYING OUT THE INEVNTION

[0078] Hereinafter, the embodiments of a process and apparatus forproducing iron carbide in accordance with the present invention isexplained together with related drawings.

[0079]FIG. 1 is a flow diagram showing the entire construction in caseof applying the present invention to an apparatus for producing ironcarbide having two reactors (two reactor stages). In FIG. 1, grainy rawmaterials (iron oxide) are charged into an ore dryer 2 as indicated byarrow 1, and said iron oxide is dried in the ore dryer 2 by hightemperature gas introduced from hot gas generator 3, and thereafter,said iron oxide is carried to first fluidized bed reactor 4.

[0080] In first fluidized bed reactor 4, the grainy iron oxide ispreliminarily reduced under fluidizing by the reducing gas introducedfrom the bottom of said reactor. The preliminarily reduced iron oxide iscarried to second fluidized bed reactor 5. In second fluidized bedreactor 5, the grainy preliminarily reduced iron oxide is furtherreduced and carburized under fluidizing by the reducing and carburizinggas introduced from the bottom of said reactor, and converted into ironcarbide. The product (iron carbide) is carried to buffer tank 6 a, 6 b,and then, transported to a melting furnace such as an electric furnaceby means of transportation such as a truck via conveyer 7.

[0081]FIG. 1 shows cyclone separator 8 a, 8 b, heat exchanger 9 a, 9 b,quenching tower 10 a, 10 b, water chiller 11, cooler 12 a, 12 b,knockout drum 13 a, 13 b which catch a drop of water and discharge itoutside, compressor 14 a, 14 b, and preheater 15 a, 15 b. As shown inFIG. 1, both first fluidized bed reactor 4 and second fluidized bedreactor 5 have the individual gas circulation loop A, B respectively.FIG. 2 illustrates that each gas passage 16 a, 16 b connected to saidgas circulation loop is lead to a supply passage of H₂ gas, CO gas, CO₂gas or natural gas (NG). In FIG. 2, the numeral 17 shows a desulfurizer.Each chamber, where is located at the lower part of first fluidized bedreactor 4 and second fluidized bed reactor 5, has two gas supply inlets(described after in detail) respectively.

[0082] Gas supply line 18 a and 18 c are connected to gas supply inletsof first fluidized bed reactor 4. Gas supply line 18 a is connected togas supply line 18 b via gas supply line 18 d. Gas supply line 18 f and18 h are connected to gas supply inlets of second fluidized bed reactor5. Gas supply line 18 e is connected to gas supply line 18 g via gassupply line 18 i. Each of gas supply line 18 a, 18 d and 18 b has gasflow control valves 19 a, 19 b and 19 c respectively. Each of gas supplyline 18 e, 18 i, and 18 g has gas flow control valves 19 d, 19 e, 19 frespectively.

[0083]FIG. 3 illustrates the detailed constitution of a first fluidizedbed reactor or a second fluidized bed reactor.

[0084] Chamber 23 locating beneath fluidized bed 22 is separated intotwo isolated parts 23 a, 23 b by separation plate 24 and each part 23 a,23 b has gas supply inlet 25 a, 25 b respectively. Fluidized bed 22 ispartitioned into division room 22 a of the upstream side and divisionroom 22 b of the downstream side by partition plate 26.

[0085] Fluidized bed 22 and chamber 23 are separated into upside anddownside by distribution plate 27. Distribution plate 27 has pluralnozzles 28 for introducing gas. The numeral 29 is an inlet for chargingraw materials and numeral 30 is an outlet for discharging the product ofiron carbide.

[0086] In this fluidized bed reactor, under fluidizing, the chargedgrainy iron oxide existing in division room 22 a of the upstream sideflows over partition plate 2 6 and flows into division room 22 b of thedownstream side. It is possible that the temperature, composition andflow rate of each gas, which is supplied to parts 23 a and 23 b ofchamber 23, may be different each other.

[0087] Process for producing iron carbide is described in more detail asfollows using the apparatus having the above mentioned constitution.

[0088] Grainy iron oxide dried in ore dryer 2 is carried into firstfluidized bed reactor 4 via passage 20, and is reduced and carburizedunder floating and fluidizing by a high temperature (approximately 650°C.) and high pressure (approximately 5 atmospheric pressure) gas beingintroduced from the bottom portion of the reactor. The reducing andcarburizing reaction consumes a large amount of H₂ and CH₄ and generatesa considerable amount of water. Consequently, the gas exhausted at about600° C. from the top of the reactor contains a considerable amount ofwater vapor. This high temperature and large moisture-containing gas iscooled along with passing through the gas circulation loop and watervapor contained in the gas is turned into water, and this water iseliminated. After that, H₂ and CH₄ is supplied to the gas circulationloop. As a result, the reaction in the fluidized bed reactor isexpedited more efficiently.

[0089] Cooling and circulation of gas in gas circulation loop A isexplained in detail hereinafter:

[0090] A reaction gas is cooled according to the following steps;

[0091] in the first steps, since a reaction gas discharged from the topof the reactor contains extremely fine particles of iron oxides, a partof fine particles of iron oxide are acquired by cyclone separation 8 a;

[0092] in the second step, a water vapor-containing gas discharged fromthe reactor at about 600° C. is cooled to 500° C. while going throughpassage 21;

[0093] in the third step, the water vapor-containing gas is cooled toabout 220° C. by heat exchanger 9 a;

[0094] in the fourth step, the gas is cooled to about 40° C. while goingthrough quenching tower 10 a to which cool water obtained at coolingtower (not shown) is supplied;

[0095] in the fifth step, the gas is cooled to about 20° C. while goingthrough cooler 12 a to which cool water generated by water chiller 11 issupplied;

[0096] in the final step, water content is eliminated from the gas atknockout drum 13 a.

[0097] The gas cooled to about 20° C. is pressurized by compressor 14 ato about 5 atmospheric pressure, and heated to about 400° C. by a hightemperature gas discharged from the reactor at heat exchanger 9 a.Further, the gas is returned into fluidized bed reactor 4 after beingheated to about 650° C. at preheater 15 a.

[0098] The gas having desirable components is supplied via a gas supplypassage as shown in FIG. 2 because the circulating gas is graduallyconsumed according to the proceeding of the reaction in the reactor.

[0099] The above mentioned reaction in a gas circulation loop A alsotakes place in a gas circulation loop B.

[0100] According to the above mentioned process, the iron oxide chargedinto first fluidized bed reactor 4 is converted to iron carbide (Fe₃C)at second fluidized bed reactor 5 and said iron carbide is dischargedfrom the reactor.

[0101] By the way, in components of iron oxide, wustite is chemicallyunstable and magnetite is chemically stable.

[0102] When the temperature of reaction gas is in the range of 500° C.to about 600° C., wustite is not generated but magnetite is generatedaccording to the equilibrium of Fe—H—O and Fe—C—O.

[0103] The iron oxide component, which remains in the product of ironcarbide, is preferably magnetite. On the other hand, it is preferable toraise the temperature of reaction gas more than about 600° C. (forexample 590° C. ) in order to increase the reaction speed. Therefore, inthis embodiment, gas supply line 18 g, which can carry some amount oflow temperature gas (gas at inlet side of preheater), is connected toline 18 h supplying gas to a division room of the downstream side. As aresult, it is possible that the temperature of gas to be supplied to adivision room of the downstream side is controlled in the range of 500°C. to 600° C. and the temperature of the gas to be supplied to adivision room of the upstream side is controlled to be over about 600°C.

[0104] As is described above, in the present invention, it is possiblethat the temperature of each gas, which is supplied to a division roomof the upstream side and a division room of the downstream side, may bedifferent each other. It is also possible to make the gas flow rate andthe gas composition for one division room different from those of theother division room in the same manner.

[0105] For example, as shown in FIG. 4 and FIG. 5, since the reducingreaction by hydrogen gas is sufficiently conducted at the mature stageof the reaction, it is desired to make the hydrogen concentrationcontained in gas to be supplied to a division room of the upstream sidelarger than that contained in gas to be supplied to a division room ofthe downstream side.

[0106] In accordance with the present invention, even if this reactionis conducted in a single fluidized bed reactor, it is possible to makethe hydrogen concentration contained in gas in the upstream sidedifferent from that contained in gas in the downstream side by means ofintroducing hydrogen gas into the gas to be supplied to a division roomof the upstream side.

[0107] Generally, the high temperature gas containing hydrocarbon suchas methane and carbon monoxide may generate a fixed carbon under acertain conduction. The fixed carbon has the following defects. One ofthe defects is that the fixed carbon consumes uselessly the reactiongas. The other defect is that the fixed carbon sticks to equipments suchas heater and the like. The another defect is that the fixed carboninvades into the material constituting the equipment, and damages saidmaterial. The fixed carbon is not generated when a large amount of wateris contained in the gas. In the conventional process for producing ironcarbide, as shown in FIG. 4 and FIG. 5, there is much water in the earlystage of reaction because of the large reducing reaction speed byhydrogen, and the fixed carbon is not easily generated. But, in thefinal stage of reaction, since the reaction speed is low, the watergenerated by the reaction is a little and fixed carbon is liable to begenerated. Consequently, in accordance with the present invention, it ispossible to raise the water concentration contained in gas to besupplied to the division room of the downstream side via line 18 g and18 h by adding steam.

[0108] It is preferable to lower the concentration of methane and carbonmonoxide contained in gas in order to prevent the generation of fixedcarbon. But, if the concentration of carbon monoxide and methane islowered, it results in the decrease of the reaction speed, namely, thelowering of the productivity. Therefore, in accordance with the presentinvention, it is possible to lower the concentration of methane andcarbon monoxide contained only in gas of the last division room of thedownstream side by means of restraining the quantity of hydrocarbon andcarbon monoxide to be introduced into gas to be supplied to the lastdivision room of the downstream side.

[0109] The specific gravity of iron oxide become lower and the diameterof iron oxide particle become smaller in accordance with the proceedingof the reaction. Therefore, the iron oxide particle at the second halfof the reaction is liable to fly. Since this flown particle is apt tostay in a short time in the reactor, the carburization degree becomeslow, and the average carburization degree of the product of iron carbidebecomes low. Accordingly, it is preferable to regulate the gas flowvelocity passing through fluidized bed according to the proceeding ofreaction. In accordance with the present invention, it is possible tolower the gas flow rate to be supplied to the division room of thedownstream side less than that to be supplied to the division room ofthe upstream side by means of controlling gas flow control valves (19a˜19 f) installed on gas supply lines.

[0110] Furthermore, in the conventional process wherein the reducingreaction is partially conducted in first reactor, and the furtherreducing and carburizing reaction are conducted in second reactor, it isnecessary to control the reduction degree of iron ore at the firstreactor. For that purpose, said control of reduction degree may beachieved by means of altering the flow rate, the temperature and thecomposition of the gas flowing in the reactor.

[0111] But it is not easy to change the above factors because of a greatdeal of gas. Consequently, it is difficult to obtain a conformable andcareful control.

[0112] In accordance with the present invention, however, it is possibleto control uniformly the gas condition to be supplied to the divisionrooms except the final division room in plural division rooms of a firstfluidized bed reactor, besides it is possible to easily alter the flowrate, the temperature and the composition of only the gas to be suppliedto the final division room.

[0113]FIG. 6 shows that fluidized bed is partitioned into division rooms22 c, 22 d, 22 e by partition plate 26 and separation plate 24separating chamber 23 is installed on the upper part of the chamber. Apart of gas introduced from gas supply inlet 25 a flows into portion 23b. Since this gas is mixed with gas introduced from gas supply inlet 25b, it is possible to make the gas component introduced into divisionroom 22 e of the downstreammost different from the gas componentintroduced division rooms 22 c and 22 d of the upstream side.

[0114]FIG. 7 shows that separation plate 24 separating chamber 23 isinstalled from the top of the chamber to the bottom thereof. Separationplate 24 has aperture 24 a in the lower part, and part 23 a iscommunicated with part 23 b via aperture 24 a. It seems that thisembodiment may achieve the same function as the embodiment shown in FIG.6.

[0115] In case of plant having the production capacity of iron carbideof more than 200,000 ton per year, it is preferable that the divisionnumber of fluidized bed is 6˜7 and the separation number of chamber istwo.

INDUSTRIAL APPLICABILITY

[0116] Since the present invention has the above constitution, theapparatus according to the present invention is suitable for theapparatus to efficiently produce iron carbide having the chemicallystable component.

1. A process for producing iron carbide by an apparatus havingconstitution elements (a) to (e); (a) a fluidized bed located at anupper part within a fludized bed reactor, and, (b) a chamber located ata lower part within the reactor to work as a gas header for introducinga reducing and carburizing gas; wherein the fluidized bed and thechamber are separated into upside and downside by a distribution plateon which multiple gas introducing nozzles are installed; and thefluidized bed located at an upper part of the distribution plate ispartitioned into plural division rooms which are formed in isolated ormazy room by a partition plate; and, (c) plural gas supply inletsarranged on the chamber for supplying gas respectively to the specificdivision room, and, connecting a gas supply line to each gas supplyinlet in order to supply a reducing and carburizing gas, wherein eachgas supply line has a gas flow control valve which controls gas pressureor gas flow rate; and, (d) one or more than two of gas circulation loopshaving a quenching tower and a cooler which eliminate dusts contained inthe exhaust gas and reduce water vapor contained in the exhaust gas, andhaving a preheater for heating the gas, wherein the exhaust gas isreturned to the chamber by way of the quenching tower, cooler andpreheater; and, (e) a gas supplying apparatus through which hydrogen gasand carbon-containing gas such as methane are supplied to a gascirculation loop; and further, comprising steps for reacting grainy ironoxide charged from a side wall of the reactor with the gas in such amanner that; the iron oxide is floated and fluidized by high temperatureand high pressure gas being introduced form the bottom portion of thereactor, and then, transferred from the division room of the upstreamside to the division room of the downstream side via a communicationspace which may locate at either upper or lower part of said partitionplate, and finally, produced iron carbide is discharged from the finaldivision room.
 2. The process for producing iron carbide of claim 1 ,wherein a chamber is separated into plural parts by separation plate andeach separated part comprises an individual gas supply inletrespectively.
 3. The process for producing iron carbide of claim 2 ,wherein a separation plate is installed at the upper part of the chamberin such a manner that only the upper part of the chamber is divided intoplural parts by said separation plate.
 4. The process for producing ironcarbide of claim 2 , wherein a separation plate is installed from thetop of the chamber to the bottom thereof for isolating each separationpart.
 5. The process for producing iron carbide of claim 2 , wherein aseparation plate is installed from the top of the chamber to the bottomthereof for separating the chamber into plural parts, and the separatedparts are communicated each other via an aperture arranged on theseparation plate.
 6. The process for producing iron carbide of claim 1 ,wherein the amount of water vapor contained in the gas to be supplied tothe division room of the downstream side is made larger than thatcontained in the gas to be supplied to the division room of the upstreamside.
 7. The process for producing iron carbide of claim 6 , wherein theamount of water vapor contained in the gas to be supplied to thedivision room of the downstream side is increased by supplying watervapor from the outside of the reactor.
 8. The process for producing ironcarbide of claim 6 , wherein the amount of water vapor contained in thegas to be supplied to the division room of the downstream side isincreased in such a manner that cooling operation of a quenching towerand a cooler in a gas circulation loop is regulated so as to decreasethe amount of removal of water vapor by said quenching tower and saidcooler.
 9. The process for producing iron carbide of claim 1 , whereinthe hydrocarbon gas or the carbon monoxide gas contained in the gas tobe supplied to the division room of the downstream side is made smallerthan that contained in the gas to be supplied to the division room ofthe upstream side.
 10. The process for producing iron carbide of claim 9, wherein the amount of the hydrocarbon gas or the carbon monoxide gascontained in the gas to be supplied to the division room of the upstreamside is increased by supplying hydrocarbon gas or carbon monoxide gasfrom the outside of the reactor more than that contained in the gas tobe supplied to the division room of the downstream side.
 11. The processfor producing iron carbide of claim 4 , wherein the gas flow rate perunit area of the gas to be supplied to the division room of thedownstream side is made smaller than that of the gas to be supplied tothe division room of the upstream side.
 12. The process for producingiron carbide of claim 1 , wherein the temperature of the gas to besupplied to the division room of the downstream side is made lower thanthat of the gas to be supplied to the division room of the upstreamside.
 13. The process for producing iron carbide of claim 12 , whereinthe temperature of the gas to be supplied to the division room of thedownstream side is made lower than that of the gas to be supplied to thedivision room of the upstream side in such a manner that a lowtemperature gas is mixed with the gas discharged from the preheater inthe gas circulation loop.
 14. The process for producing iron carbide ofclaim 13 , wherein the low temperature gas is a part of the gas to besupplied to a preheater.
 15. The process for producing iron carbide ofclaim 13 , wherein the low temperature gas is to be supplied from theoutside of the reactor.
 16. The process for producing iron carbide ofclaim 12 , wherein the temperature of the fluidized bed in the divisionroom of the downstream side is made in the range of 500˜600° C.
 17. Theprocess for producing iron carbide of claim 16 , wherein the temperatureof the fluidized bed in the last division room of the downstream side ismade in the range of 500˜600° C. by decreasing the temperature of onlythe gas to be supplied to the last division room of the downstream side.18. The process for producing iron carbide of claim 12 , wherein thetemperature of the gas to be supplied to the division room of thedownstream side is made lower than that of the gas to be supplied to thedivision room of the upstream side in such a manner that oxygen is mixedwith the gas to be supplied to the division room of the upstream side,and then, a part of combustible gas contained in said gas is partiallyburned in order to raise the gas temperature.
 19. The process forproducing iron carbide of claim 4 , wherein the concentration ofhydrogen contained in the gas to be supplied to the division room of theupstream side is made higher than that of hydrogen contained in the gasto be supplied to the division room of the downstream side.
 20. Theprocess for producing iron carbide of claim 19 , wherein theconcentration of the hydrogen in the gas to be supplied to the divisionroom of the upstream side is increased by supplying hydrogen gas fromthe outside of the reactor.
 21. An apparatus for producing iron carbidecomprising the constitution elements (a) to (e); (a) a fluidized bedlocated at an upper part within a fludized bed reactor, and, (b) achamber located at a lower part within the reactor to work as a gasheader for introducing a reducing and carburizing gas; wherein thefluidized bed and the chamber are separated into upside and downside bya distribution plate on which multiple gas introducing nozzles areinstalled; and the fluidized bed located at an upper part of thedistribution plate is partitioned into plural division rooms which areformed in isolated or mazy room by partition plate; and, (c) plural gassupply inlets arranged on the chamber for supplying gas respectively tothe specific division room; and, connecting a gas supply line to eachgas supply inlet in order to supply a reducing and carburizing gas;wherein each gas supply line has a gas flow control valve which controlseach gas pressure or gas flow rate; and, (d) one or more than two of gascirculation loop having a quenching tower and a cooler which eliminatedusts contained in the exhaust gas and reduce water vapor contained inthe exhaust gas, and having a preheater for heating the gas, wherein theexhaust gas is returned to the chamber by way of the quenching tower,cooler and preheater; and, (e) a gas supplying apparatus through whichhydrogen and carbon-containing gas such as methane are supplied to saidgas circulation loop.